With HSP its easy to automatically benefit from the advantages of SSDs compared to a harddisk-only solution. A system using HSP can be both faster and cheaper than the latter. See this link for some nice examples and more details.

I was just updating the kernel and looking at the new stuff that has been added, and
there is now a 'CACHEFILES' option which allows for caching (usually remote) filesystems to a local filesystem. I guess I could use this to cache a slower storage mechanism (HDD) to a faster one (SSD), at least for one level of hierarchy.

The OHSM project looks like an interesting one to follow. Only ext2 and the 2.6.30 kernel is supported for now, but I expect if it works out well then this will gain more filesystems.
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David GardnerJan 22 '10 at 11:41

That project looks abandoned, most recent activity was in 2009.
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sendmoreinfoSep 12 '11 at 22:05